Diabetes insipidus - central

Definition

Alternative Names

Central diabetes insipidus

Causes, incidence, and risk factors

Central diabetes insipidus occurs when the body has too little of the hormone vasopressin.

Vasopressin limits the amount of urine the body produces. Normally, the hypothalamus gland in the brain makes vasopressin, and the pituitary gland stores the hormone. Without vasopressin, the kidneys do not work properly to keep enough water in the body. The result is a rapid loss of water from the body in the form of dilute urine. A person with diabetes insipidus needs to drink large quantities of water, driven by extreme thirst, to make up for this excessive water loss in the urine (as much as 20 liters per day).

The reduced levels of vasopressin associated with central diabetes insipidus may be caused by damage to the hypothalamus or pituitary gland. This damage may be related to surgery, infection, inflammation, tumor, or injury to the head.

Sometimes the cause remains unknown. Very rarely, central diabetes insipidus can be caused by a genetic defect.

Symptoms

Confusion and changes in consciousness due to dehydration (if the patient is unable to drink)

Signs and tests

A person with central diabetes insipidus produces more than 3 liters of urine a day. Urinalysis will show a low concentration of salt in the urine.

A water restriction test is used to look at how well the kidney works and how much urine is produced. The person is not allowed to drink any water or fluids. This test is done during a hospital stay. It tells the difference between someone who is making urine because of drinking a lot of liquid and someone who is not. If you have central diabetes insipidus, you will still make a lot of urine even when fluids are not given.

Another test involves giving the person vasopressin. This helps tell the difference between central and nephrogenic diabetes insipidus.

A CT or MRI of the head may show a problem in or near the pituitary gland.

Treatment

The cause of the underlying condition should be treated.

Vasopressin (desmopressin) may be given either as a nasal spray, tablets by mouth, or injections under the skin. This controls the urine output and fluid balance and prevents dehydration.

In mild cases, drinking more water may be all that is needed. If the thirst mechanism is not working (for example, if the hypothalamus is damaged), a prescription for a certain amount of water intake may also be needed (usually 2 - 2.5 liters per day) to ensure proper hydration.

Expectations (prognosis)

The outcome depends on the cause. If treated, central diabetes insipidus usually does not cause severe problems or result in early death.